During the processing of photographic materials, one or more rinsing or washing steps may be used to remove residual processing solution from the materials prior to contact with the next processing solution. Moreover, before processed materials are dried, they are generally washed a last time to remove all remaining chemical residues so that when they are dried, they are free of lines, water spots or scum. For example, in processing most films and papers (both color and black and white), a final rinsing or stabilizing step is used prior to drying.
Many different formulations have been proposed for use as final rinse solutions in photographic processes immediately prior to drying. Generally, they include one or more surfactants that facilitate the "cleaning" of the photographic material and uniform liquid drainage. Some final processing solutions also contain dye image stabilizers and are thusly known as stabilizing solutions. In addition, rinse or stabilizing solutions can contain one or more biocides to prevent unwanted biological growth in the processing tank or on the photographic material. The solutions may additionally contain calcium ion sequestering agents or polymers such as polyvinylpyrrolidone to reduce precipitation of sulfur or sulfides.
To meet all of the needs of a final processing solution, a careful formulation of components, generally surfactants and biocides, must be made. Proper balancing is required to keep costs low, minimize foaming and biological growth, while achieving the desired drainage and defect free processing expected by highly critical customers.
For final processing solutions that are dye image stabilizing solutions, the presence of a dye image stabilizer further complicates the formulation needs. Dye image stabilizers typically have a methylene group (or is capable of producing a methylene group) that prevents redox degradation of certain magenta dye forming couplers. Thus, dye stain can be reduced or dye image enhanced with such solutions. Typical stabilizers include aldehydes, such as formaldehyde. Hexamethylenetetramine (HMTA) is a known substitute for formaldehyde because of its lower volatility. The addition of the stabilizer, and the type of stabilizer, can render some conventional surfactants in final rinse solutions ineffective in washing scum and other residue from the processed films.
Not every final processing solution (either final rinse or stabilizing solution) useful for processing one type of photographic element may be useful for processing other types of elements. Each type of photographic element may have surface characteristics, or be processed using unique chemicals that require unique final processing solution components.
For example, stabilizing solutions useful to process many conventional color negative films can contain an aldehyde) such as formaldehyde or a benzaldehyde) or hexamethylenetetramine (HMTA) and one or more surfactants, including a mixture of a nonionic surfactant and an anionic surfactant. Such processing solutions are described, for example, in U.S. Pat. No. 3,676,136 (Mowrey), U.S. Pat. No. 4,786,583 (Schwartz), U.S. Pat. No. 5,529,890 (McGuckin et al) and U.S. Pat. No. 5,578,432 (McGuckin et al) and EP-A-0 530 832 (Koma et al). In addition, recently allowed and commonly assigned U.S. Ser. No. 08/639,858 (filed Apr. 19, 1996, by McGuckin et al) describes the use of HMTA and mixtures of surfactants, including fluorinated nonionic surfactants, in final processing solutions for photographic films having a magnetic backing layer.
However, it has been observed that such stabilizing solutions are not always useful when processing a variety of commercial photographic films including those having a magnetic recording layer on one side of the polymeric film support. Thus, there is a continuing need in the art for an improved, low cost, effective, formaldehyde-free and non-scumming photographic stabilizing solution that achieves all of the desired results when various films are processed in various processing machines.